Several techniques providing coordinate input functions in display apparatuses themselves have been proposed.
Specifically, for example, a display apparatus using a pressure sensitive type touch panel system (see, for example, Patent Documents 1 and 2) and a display apparatus using an electromagnetic induction type touch panel system (see, for example, Patent Document 3) are known.
However, a display apparatus having coordinate input function means as described above, had the problems that miniaturization was difficult, and costs became higher in comparison with ordinary display apparatuses.
Therefore, in recent years, there have been being actively developed display apparatuses for overcoming the above problem, in which a light receiving element is provided to each pixel of the display apparatus, and incident light upon the light receiving element is detected to specify coordinates inside the display apparatus (see Patent Documents 4 and 5).
An apparatus providing light receiving elements so as to enable input of coordinates in a display apparatus as described above, not only has the advantage that the size can be reduced and costs can be lowered in comparison with a display apparatus provided with a coordinate input function means, but also enables multi-point coordinate input and area input.    Patent Document 1: Japanese Patent Publication (A) No. 2002-149085    Patent Document 2: Japanese Patent Publication (A) No. 2002-41244    Patent Document 3: Japanese Patent Publication (A) No. H11-134105    Patent Document 4: Japanese Patent Publication (A) No. 2004-318067    Patent Document 5: Japanese Patent Publication (A) No. 2004-318819